Most Popular

Overall, the study found that electricity used for pumping, treating, heating and cooling water accounted for 12.6 percent of the nation's energy use in 2010. The amount is equivalent to the annual energy usage of roughly 40 million Americans, the report concluded.

“This ends up being a big number,” Webber said. “It's bigger than people expected.”

Kelly Twomey Sanders, one of the study's authors, said the findings set a baseline at a time when Texas, California and other states are looking at more energy-intensive ways to deliver water, such as desalination plants and pipelines that bring water from remote river basins to more populated areas.

“Although these shifts are likely to have an appreciable impact on future energy demand, very little analysis has been done to quantify water-related energy use at the national level,” she said. “This analysis serves to fill that gap.”